The present invention relates generally to semiconductor substrates, and more specifically to non-straight edged substrates for use in medical devices.
Traditionally, integrated circuit substrates and integrated circuit dice are cut or scribed from larger pieces of material in known shapes. Cutting and scribing implements for such dice and substrates are only capable of cutting or scribing along a straight line. The resulting substrates and dice formed by traditional cutting and scribing are, therefore, comprised of all straight line edges. Traditional shapes for such dice and substrates are rectangles and parallelograms, although other polygonal shapes such as octagons and the like have been used. However, all the resultant dice and substrates typically comprise of straight edges.
Such straight edges are preferred for use in semiconductor fabrication, because arrangement of the integrated circuits and the like is made easier by having similar shapes. However, in certain areas, such as the field of implantable medical devices, substrates and even integrated circuits are held to extremely tight size specifications. Since the overall trend in implantable medical devices is toward smaller and smaller sizes, and since rough edges and sharp corners are preferably avoided in many implantable medical devices (IMDs), substrates in IMDs often have wasted space and volume due to rounded edges, and have real estate on the die that is unavailable for use due to the restraints on integrated circuit shapes.
Silicon devices and substrates have traditionally been scribed and broken along cleavage planes, or diced in straight lines with a diamond impregnated cutting blade. As such, the edges of the resultant dice and devices are generally straight. For packing efficiency, it is desirable to use an electronic module or substrate that exactly or very closely matches the shape of the product to be developed or used. However, many electronic devices, especially in the implantable medical device field, are not cubic or box-shaped. Instead, they can take on many different shapes, often with curved edges and contours. From an IMD device standpoint, cubes and boxes are not a good match. From a design perspective, however, straight edge devices are not desirable. Further, since curved edges are prominent in IMDs, rectangular silicon devices and substrates are inefficient from a packaging density standpoint.
Silicon has a number of benefits as a substrate material, in that it is readily available, and also processes and methods for preparing and working with Silicon are known in the art.
In one embodiment, a substrate for an implantable medical device includes a substrate body formed to conform to the shape of the implantable medical device, and a number of integrated circuits formed on the body. The integrated circuits are in another embodiment formed to fit the contoured edges of the substrate.
In another embodiment, an implantable medical device includes a body and a substrate positioned in the body, the substrate having medical device circuitry formed thereon. The substrate has edge contours formed to fit the interior dimension of the substrate body.
In still another embodiment, method for improving package density in an implantable medical device includes creating a free formed substrate shaped with curved edge contours to conform to interior edges of a body of the implantable medical device, and forming integrated circuits on the free formed substrate to use previously unused portions of the substrate.